1. Field of the Invention
The invention relates generally motor control systems, and more specifically to a vehicle door positioner power supply system that has a reduced power supply current requirement.
2. Background of the Invention
Automatic vehicle door opening and closing mechanisms are in widespread use in public transportation systems such as trains and buses, as well as in private vehicles adapted for use by the handicapped. The control of the operation of a vehicle door is typically performed by an electronic control system that determines the position and speed of a moving element of an electric motor that operates the door positioning mechanism.
An example of a conventional vehicle door apparatus is described in “Development of linear motor drive door system for commuter train”, Sato, et al., Papers delivered in the Convention held by the Industrial Application Section of The Institute of Electrical Engineers of Japan, 1999, The Institute of Electrical Engineers of Japan, 1999, at p. 359 to 362. In the above-referenced paper, the maximum output voltage of the inverter supplying power to the door motor is proportional to the power source voltage of the vehicle power distribution system. Therefore, when the power source voltage is lowered, the maximum voltage that can be supplied to the motor from the inverter is also lowered. Therefore, it is necessary to increase the rated current of the motor to obtain a given motor output when lower power supply voltages will be encountered. It is also necessary to increase the diameter of the wiring supplying power to the electric motor in order to avoid excessive voltage drop, adding cost and weight to the vehicle.
Therefore, it would be desirable to provide a vehicle door positioner power supply system that supplies the maximum output voltage of an inverter to a motor without being influenced by the fluctuation of the power source voltage, thereby reducing the cost and weight of the vehicle. It would further be desirable to provide a vehicle door positioner power supply system that reduces power consumption.